Interpreting Ix Results

Question 1

How do you calculate the anion gap from blood gas results?

Answer 1

(sodium + potassium) - (bicarbonate + chloride)

Question 2

What is a normal anion gap?

Answer 2

8-14 mmol/L

Question 3

What causes of metabolic acidosis would present with a normal anion gap?

Answer 3

• gastrointestinal bicarbonate loss: diarrhoea, ureterosigmoidostomy, fistula
• renal tubular acidosis
• drugs: e.g. acetazolamide
• ammonium chloride injection
• Addison’s disease

Question 4

What causes of metabolic acidosis would present with a raised anion gap?

Answer 4

• high lactate: shock, hypoxia
• high ketones: diabetic ketoacidosis, alcohol
• high urate: renal failure
• high 5-oxoproline: chronic paracetamol use, acute paracetamol toxicity, congenital (GSD)
• acid poisoning: salicylates, methanol